Topic 6: The Rate and Extent of Chemical Change

How is rate of reaction calculated?

Rate = amount of reactant used ÷ time

or

Rate = amount of product formed ÷ time

What units are used for rate of reaction?

g/s, cm³/s, or mol/s

How can you determine rate from a graph?

Draw a tangent to the curve and calculate the gradient.

Name 5 factors that affect the rate of reaction.

Temperature, concentration, pressure, surface area, and catalysts.

What does collision theory state?

Reactions only occur when particles collide with enough energy.

What is activation energy?

The minimum amount of energy required for a reaction to occur.

How does increasing temperature affect rate?

Increases collision frequency and energy, increasing rate.

How does increasing concentration or pressure affect rate?

More particles in the same space, so more frequent collisions.

How does increasing surface area affect rate?

More area exposed for collisions = faster reaction.

What is a catalyst?

A substance that increases rate of reaction without being used up.

How does a catalyst work?

It provides an alternative reaction pathway with lower activation energy.

What is a reversible reaction?

A reaction where products can react to form the original reactants.

What symbol represents a reversible reaction?

⇌

If a reversible reaction is exothermic in one direction, what is the other direction?

Endothermic

What is dynamic equilibrium?

When the forward and reverse reactions occur at the same rate in a closed system.

What does Le Chatelier’s Principle state?

If conditions change, the system shifts to oppose the change.

What happens if you increase the concentration of reactants at equilibrium?

The position of equilibrium shifts to make more products.

What happens if temperature increases in a reversible reaction?

The equilibrium shifts in the endothermic direction.

What happens to equilibrium if pressure is increased in a gas reaction?

It shifts to the side with fewer gas molecules.

How does decreasing pressure affect gaseous equilibrium?

Shifts to the side with more gas molecules.